Extracellular Polymeric Substances Level Determines the Sludge Dewaterability in Bioleaching Process

Reasons for Ineffectiveness in Improving Dewaterability of Anaerobically Digested Sludge by Bioleaching

“…Acidophilic chemoautotrophic bacterium Acidithiobacillus ferrooxidans LX5 (CGMCC No. 0727) obtained from China General Microbiological Culture Collection Center (CGMCC) was cultured in modified 9K medium [12]. The modified Fe 2+ -free 9K medium was acidified with sulfuric acid to pH 2.5, then autoclaved at 121 • C for 15 min.…”

“…The bioleaching process using the Acidithiobacillus species, previously explored for removing sludge-borne heavy metals [7][8][9], is now being applied to improving dewaterability of sludge as a novel bio-conditioning technique [10][11][12]. In this process, bacteria from the genus Acidithiobacillus (such as Acidithiobacillus ferrooxidans) are capable of oxidizing ferrous iron to ferric iron and lowering the sludge pH, thus creating favorable conditions for flocculation and dewatering of the sludge flocs.…”

“…Previous studies have shown that the bioleaching process followed by a diaphragm pressure filter can reduce the moisture content of undigested waste-activated sludge to less than 60% without adding macromolecular flocculants, e.g., polyacrylamide. More than 20 sludge bioleaching plants, with a total processing capacity of nearly 6000 t/d of sludge (equivalent to 80% moisture content), have realized commercial operations in China since 2010 [10,12]. The moisture content of bioleached sludge after mechanical dewatering was easily decreased to 60% or below [13].…”